A few Tumblr feeds I have tried seem to have as many or more photos of guys nude or having sex. Are any of the above mentioned.. or other.. tumblr feeds strictly focused on the swimwear?

They are mostly dedicated to Speedos (brief swimwear and underwear). They do have some nude pics, but mostly shirtless hunks in skimpy bottoms. Check it out, don't check it out. Just listing some of my favorites.